Millions of people die or are disabled each year from acute stroke or heart attack that is caused by the highly localized formation of blood clots resulting in occlusion of the carotid or coronary arteries. In cases where premonitory symptoms or signs of disease indicate the risk of an acute event, a cocktail of various anticoagulants and antiplatelet agents is administered both orally and intravenously to prevent clot progression. Even with aggressive treatment regimens, however, thrombus formation may still proceed unpredictably. Additionally, severe or fatal bleeding problems may arise with the systemically active anticoagulants in use today. Accordingly, there is a need in the art for the development of safer and more effective antithrombotics.